Soil testing - the real cost to growers

November 09, 2007|By Dave Franzen, NDSU Soil Specialist

Soil testing is not used as regularly across North Dakota as it should be. It is the only number that represents a real portion of nitrogen (N) that growers can count on to factor into their N fertilizer rate decision. There are some growers who do not use soil testing because it is "too expensive." But an analysis of soil testing, if the grower samples his/her field, reveals that sampling pays off. However, we need to start with some assumptions:

Anhydrous ammonia is $500 per ton (31 cents a pound of N)

Urea is $370 per ton (41 cents per pound of N)

Nitrate-N analysis is $4.50 per sample

A full suite of soil nutrients is $14.50 per sample

Field size per sample is 80 acres

The price of wheat is $7.50 per bushel

The price of corn is $3 per bushel The soil test itself is almost negligible in cost. To pay for soil testing, the grower only requires 11 to 14.5 pounds of N savings for an entire 80-acre field to pay for it, or 0.6 bushel of wheat or 1.5 bushels of corn for the entire field. However, most soil testing is conducted by a consultant. Let's assume that the consultant will take a composite soil test with the suite of nutrients across the 80-acre field for $2 per acre. Our other assumptions will stay the same. For 4.9 to 6.5 pounds of N per acre, or about 1/4 bushel of wheat or 2/3 bushel of corn per acre, a grower easily can hire a consultant to soil test an 80-acre field and provide a good guide to determining nitrogen and other nutrient rates for the field. Soil testing always has paid, but this year it will pay more than ever.